U.S. patent number 4,340,812 [Application Number 06/131,693] was granted by the patent office on 1982-07-20 for radiation energy collection and tracking apparatus.
Invention is credited to Kei Mori.
United States Patent |
4,340,812 |
Mori |
July 20, 1982 |
Radiation energy collection and tracking apparatus
Abstract
A light energy collection apparatus comprising an optical system
for collecting the light energy, a framework for supporting the
optical system, a tracking device for driving the supporting
framework so as to normally keep the optical system pointed at a
light source, an optically transparent housing enclosing the
optical system and the tracking device as well, a structure for
supporting the housing and if required a means for converting the
collected light energy into electrical or thermal energy.
Inventors: |
Mori; Kei (Setagaya-ku, Tokyo,
JP) |
Family
ID: |
27572164 |
Appl.
No.: |
06/131,693 |
Filed: |
March 19, 1980 |
Foreign Application Priority Data
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Mar 26, 1979 [JP] |
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54-34243 |
Mar 31, 1979 [JP] |
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54-37732 |
Mar 31, 1979 [JP] |
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54-37733 |
Jul 5, 1979 [JP] |
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54-84406 |
Nov 8, 1979 [JP] |
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54-144662 |
Nov 8, 1979 [JP] |
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54-144663 |
Nov 13, 1979 [JP] |
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54-146962 |
Nov 22, 1979 [JP] |
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54-151392 |
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Current U.S.
Class: |
250/203.1;
126/577; 250/203.4; 126/698; 359/591 |
Current CPC
Class: |
F21S
11/00 (20130101); G01S 3/7861 (20130101); F24S
30/458 (20180501); F24S 23/12 (20180501); F24S
23/30 (20180501); Y02E 10/47 (20130101); F24S
2030/136 (20180501); F24S 2030/134 (20180501) |
Current International
Class: |
F24J
2/54 (20060101); F24J 2/08 (20060101); F24J
2/06 (20060101); F24J 2/00 (20060101); G01S
3/786 (20060101); G01S 3/78 (20060101); G01J
001/20 () |
Field of
Search: |
;250/23R,209,227,216
;126/424,425 ;350/258,262,264 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelms; David C.
Attorney, Agent or Firm: Burgess, Ryan and Wayne
Claims
What is claimed is:
1. A light energy collection apparatus comprising:
an optical system for collecting light energy from a light source,
comprising:
a lens system for converging the light energy,
an optical coupler upon which the light energy is focused through
said lens system, and
a light-guide cable with one end connected to said optical coupler
so that the light energy focused on said optical coupler enters
said light-guide cable,
a supporting framework for supporting said optical system;
a tracking device for driving said supporting framework in such a
way that the optical system is normally kept pointed at said light
source, said tracking device comprising:
a main shaft supported for rotation,
one or more light energy collectors each mounted on said main shaft
for rotation about an axis perpendicular to the axis of said main
shaft, and
means for rotating said one or more light energy collectors about
their axes of rotation;
a device for detecting the position of said light source, said
device including a weight mechanism mounted on said main shaft in
such a way that regardless of the angular position of said main
shaft, said weight mechanism is normally vertically oriented;
a spherical lens mounted on said weight mechanism, and a plurality
of optical sensors situated at the focal points of said spherical
lens,
whereby in response to the outputs from said optical sensors, the
direction or position of said light source is detected;
an optically transparent housing enclosing said optical system and
said tracking device; and
a supporting means for supporting said housing.
2. A light energy collection apparatus comprising:
an optical system for collecting light energy from a light
source;
a converter means for converting the collected light energy into
electrical or thermal energy;
a supporting framework for supporting said optical system and said
converter means;
a tracking device for driving said supporting framework in such a
way that the optical system is normally kept pointed at said light
source, said tracking device comprising:
a main shaft supported for rotation,
one or more light energy collectors each mounted on said main shaft
for rotation about an axis perpendicular to the axis of said main
shaft, and
means for rotating said one or more light energy collectors about
their axes of rotation;
a device for detecting the position of said light source, said
device including a weight mechanism mounted on said main shaft in
such a way that regardless of the angular position of said main
shaft, said weight mechanism is normally vertically oriented;
a spherical lens mounted on said weight mechanism, and a plurality
of optical sensors situated at the focal points of said spherical
lens,
whereby in response to the outputs from said optical sensors, the
direction or position of said light source is detected;
an optically transparent housing enclosing said optical system and
said tracking device; and
supporting means for supporting said housing.
3. A light energy collection apparatus, comprising:
a rotatable lens system for converging radiation from a light
source;
tracking means for rotating said lens system to track said light
source;
a rotatable main shaft for supporting said lens system;
a first light-guide cable mounted for rotation with said main
shaft, said cable having a light input end disposed in the focal
region of said lens system for receiving light energy therefrom,
and a light output end; and
a second relatively stationary light-guide cable having a light
input end adjacent to, coaxial with and optically coupled to the
light output end of said first light-guide cable, said second
light-guide cable having a light delivery end remote from the light
input end thereof for illuminating a region remote from said lens
system.
4. The apparatus according to claim 3, wherein said lens system is
rotatable about two mutually orthogonal axes, the weight of said
lens system being balanced with respect to each of said axes so
that the power required for rotating said lens system is
minimized.
5. The apparatus according to claim 3, wherein said light output
end of said first light-guide cable is disposed within and coaxial
with said main shaft.
6. The apparatus according to claim 3, wherein said tracking means
rotates said main shaft through a worm, a worm wheel in mesh with
said worm, and a torque limiter means interposed between said main
shaft and said worm wheel.
7. The apparatus according to claim 3, 4, 5 or 6, wherein the light
input end of said first light-guide cable comprises a plurality of
light transmissive layers having different refractive indices.
8. The apparatus according to claim 3, 4, 5 or 6, wherein said
light input end of said first light-guide cable comprises a
plurality of optical fibers in intimate contact with each other,
each of said fibers having a hexagonal cross-section.
9. A light energy collection apparatus as set forth in claim 3, 4,
5 or 6, wherein said input end of said first light-guide cable has
a refractive-index gradient which is gradually increased from the
input end to the output end thereof.
10. A light energy collection apparatus as set forth in claim 3,
wherein adjacent ends of said second light-guide cable and another
light-guide cable are formed with rectangular cross-sections, and
with ridges and recesses in each of said adjacent ends respectively
in parallel with the direction of transmission of light energy,
with said adjacent ends being intermeshed to form a joint for
end-to-end connection or branching.
11. A light energy collection apparatus, comprising:
a lens system rotatable about two mutually orthogonal axes and
supported by a main shaft, for converging radiation from a light
source, the weight of said lens system being balanced with respect
to each of said axes so that the power required for driving said
lens system is minimized;
tracking means for rotating said lens system to track said light
source, said tracking means comprising one or more light energy
collectors each mounted on said main shaft for rotation about the
axis perpendicular to the axis of said main shaft, and a means for
rotating said one or more light energy collectors about their axes
of rotation; and
light transmission means including a light-guide cable having a
light receiving end and a light distribution end for coupling light
from said lens system to illuminate a region remote therefrom.
12. The apparatus according to claim 11, wherein said tracking
means rotates said main shaft through a worm, a worm wheel in mesh
with said worm, and a torque limiter means interposed between said
main shaft and said worm wheel.
13. The apparatus according to claim 11 or 12, wherein the light
receiving end of said light-guide cable comprises a plurality of
light transmissive layers having different refractive indices.
14. The apparatus according to claim 11 or 12, wherein said light
input end of said first light-guide cable comprises a plurality of
optical fibers in intimate contact with each other, each of said
fibers having a hexagonal cross-section.
15. A light energy collection apparatus, comprising:
a lens system rotatable about two mutually orthogonal axes and
supported by a main shaft, for converging radiation from a light
source, the weight of said lens system being balanced with respect
to each of said axes so that the power required for driving said
lens system is minimized;
tracking means for rotating said lens system to track said light
source, said tracking means comprising one or more light energy
collectors each mounted on said main shaft for rotation about the
axis perpendicular to the axis of said main shaft, and a means for
rotating said one or more light energy collectors about their axes
of rotation through a worm, a worm wheel in mesh with said worm,
and a torque limiter means interposed between said main shaft and
said worm wheel; and
a first light-guide cable mounted for rotation with said main
shaft, said cable having a light input end disposed in the focal
region of said lens system for receiving light energy therefrom,
and a light output end; and
a second relatively stationary light-guide cable having a light
input end adjacent to, coaxial with and optically coupled to the
light output end of said first light-guide cable, said second
light-guide cable having a light delivery end remote from the light
input end thereof for illuminating a region remote from said lens
system.
16. The apparatus according to claim 15, wherein said light output
end of said first light-guide cable is disposed within and coaxial
with said main shaft.
17. The apparatus according to claim 15 or 16, wherein the light
input end of said first light-guide cable comprises a plurality of
light transmissive layers having different refractive indices.
18. The apparatus of claim 15 or 16, wherein said light input end
of said first light-guide cable comprises a plurality of optical
fibers in intimate contact with each other, each of said fibers
having a hexagonal cross-section.
19. A light energy collection apparatus as set forth in claim 3, 11
or 15, wherein
said tracking means comprises at least one pair of optical sensors
located in the same plane between said lens system and the focal
point thereof and adjacent to the beam of the light energy being
converged through said lens system; and
said lens system is driven by said tracking means so that the
output signals from said pair of optical sensors are normally
balanced with each other.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a novel apparatus for collecting
the radiant energy such as light energy, and especially solar
energy.
Extensive studies and experiments for utilization of solar
radiation have been being made in order to solve the increasing
energy problem, but the fact that the solar constant is as small as
about one kilowatt per square meter presents very serious problems.
In addition, it is impossible to convert the solar energy collected
into other useful energies such as electricity or heat without
conversion losses. Even when the sunlight collected is used for
illumination without any conversion, there arises the problem of
transmission losses. Furthermore, with the conventional solar
energy collectors with a low efficiency, a huge sunlight collecting
area must be provided. In addition, the sites for installation of
such huge sunlight collectors are limited on the earth in view of
climatic and geographic conditions.
Meanwhile there have been recently proposed various projects for
underwater farms and ranches, and the use of sunlight at such
underwater farms and ranches will attain very advantageous results
in cultivation of various vegetables, animals and fish. If the
sunlight collectors can be deployed in the sea immediately above
the underwater farms and ranches, the problem of transmission
losses will be overcome to a satisfactory degree. In addition, the
problems encountered when the sunlight collectors are installed on
the land will be also solved.
OBJECTS OF THE INVENTION
The primary object of the present invention is therefore to provide
a light energy collection apparatus which can collect the
low-energy-density solar energy with a high efficiency and transmit
the collected solar energy to the desired places such as underwater
farms and ranches through a transmission line of a short length
with minimal transmission losses.
Another object of the present invention is to provide a tracking
device which can normally maintain an optical system for collecting
solar energy pointed at the sun, so that a high efficiency of
collection of solar radiation can be attained.
A further object of the present invention is to provide a solar
energy collection apparatus in which one or more solar energy
collectors are normally kept pointed at the sun; but when wind
gusts or the like exert excessive forces on them, the connection
between the solar energy collectors and tracking device is released
so that the breakdown of or damage to the solar energy collection
apparatus can be avoided.
A further object of the present invention is to provide an
automatic tracking device which enables the optical system to
precisely follow the diurnal motion of the sun from sunrise to
sunset throughout the four seasons.
A still further object of the present invention is to provide a
device for precisely detecting the position of a light source or
the sun so that the light or solar energy collection apparatus can
precisely follow the motion of the light source or the diurnal
motion of the sun.
A further object of the present invention is to provide an optical
coupler which may couple one optical system to another with a
minimum degree of transmission loss.
A yet further object of the present invention is to provide a
light-guide cable with the input end capable of receiving the light
rays with a minimum degree of transmission loss.
A still further object of the present invention is to provide a
junction for connecting a light-guide cable end-to-end to another
or for branching into a plurality of light guides.
The above and other objects, effects, features and advantages of
the present invention will become more apparent from the following
description of some preferred embodiments thereof taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view of a first embodiment of a
solar energy collection apparatus in accordance with the present
invention;
FIG. 2 is a side view of a second embodiment of the present
invention;
FIG. 3 is a top view of a solar energy collector of the solar
energy collection apparatus shown in FIG. 2;
FIG. 4 is a front view thereof;
FIG. 5 is a top view of a third embodiment of the present
invention;
FIG. 6 is a side view looking in the direction indicated by the
arrow V of FIG. 5;
FIG. 7 is a side view looking in the direction indicated by the
arrows VI of FIG. 5;
FIG. 8 is a schematic side view of a fourth embodiment of the
present invention;
FIG. 9 is a perspective view of a fourth embodiment of the present
invention;
FIG. 10 is a partial front view, on enlarged scale, thereof showing
the connection between a motor 128 and a shaft 126;
FIG. 11 is a side view of a fifth embodiment of the present
invention;
FIG. 12 is a partial axial sectional view, on enlarged scale,
thereof showing the connection between a main shaft 201 and a
driving motor (not shown) for driving the same;
FIG. 13 is a sectional view of a sixth embodiment of the present
invention or more particularly an automatic tracking device;
FIG. 14 is a sectional view taken along the line I--I of FIG.
13;
FIG. 15 is a diagram used for the explanation of the underlying
principle of the automatic tracking device shown in FIGS. 13 and
14;
FIG. 16 is a sectional view of a seventh embodiment of the present
invention;
FIG. 17 shows on the same plane both the cross sections taken along
the lines I--I and II--II of FIG. 16;
FIG. 18 is a perspective view of an eighth embodiment of the
present invention or more specifically a device for detecting the
position of the sun;
FIG. 19 is a sectional view of a ninth embodiment of the present
invention;
FIG. 20 is a longitudinal sectional view of an optical coupler used
in the solar energy collector shown in FIG. 19;
FIG. 21 is a cross sectional view of a prior art or conventional
light-guide cable;
FIG. 22 is a sectional view of the input end of a light-guide cable
in accordance with the present invention;
FIG. 23 is a layout of light-guide cables connected in accordance
with the present invention;
FIG. 24 shows, in perspective view, the ends of the light-guide
cables which are to be joined;
FIG. 25 is a cross sectional view of the light-guide cables shown
in FIG. 24;
FIG. 26 shows, in cross section, the ends to be connected of the
light-guide cables;
FIG. 27 is a longitudinal sectional view taken along the line V--V
of FIG. 25 and showing the light-cables joined;
FIG. 28 is a perspective view of a modification of the joint
preparation of the light-guide cable;
FIG. 29 is a longitudinal sectional view showing the joint between
the light-guide cables with the end preparation shown in FIG. 28;
and
FIG. 30 is a longitudinal sectional view showing the light-guide
cable branched from the light-guide cable according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment, FIG. 1
In FIG. 1 is shown a first embodiment of an apparatus for
collecting solar energy in accordance with the present invention.
The apparatus includes an optical system 10 for collecting the
solar energy and a buoy 20 upon which is mounted the optical system
10. The optical system 10 comprises a lens 11 for focusing the
solar energy, a photoelectric element 12 for converting the solar
energy into electrical energy, a light-guide cable 13 for the
transmission of the collected solar energy, a supporting framework
14 which supports the lens 11, the photoelectric element and the
light-guide cable 13 and which is adapted to rotate about the
horizontal and vertical axes 15 and 16 so as to keep both the lens
11 and the photoelectric element 12 pointed at the sun, a spherical
casing or dome 17 which is made of a transparent material such as
acrylic resins and which encloses therein the supporting framework
14 and a heat radiator 18 consisting of a plurality of fins.
In addition to the optical system 10, the buoy 20 carries batteries
22 and control units 23 and includes a ring-shaped float 21. The
solar energy collection apparatus therefore may float in the sea
water.
The supporting framework 14 is rotated about the horizontal and
vertical axes 15 and 16 by the control units 23 so that the lens 11
and the photoelectric element 12 may be normally kept pointed at
the sun as described elsewhere. The horizontal and vertical axes or
shafts 15 and 16 which are mutually perpendicular are so arranged
as to pass through the center of the spherical casing or dome 17,
whereby the weights are balanced relative to the shafts 15 and 16
respectively and, consequently, a relatively small driving force is
needed to keep the supporting framework 14 and hence the lens 11
and the photoelectric element 12 tracking the sun. It is preferable
to seal nitrogen gas or the like in the spherical casing or dome 17
so as to prevent the overheating and the degradation of the
components by oxidation in the dome 17.
The solar energy focused through the collection lens 11 at one end
of the light-guide cable 13 is transmitted therethrough and through
a light-guide cable 13' connected to the former to an underwater
farm, ranch or the like. However, the buoy 20 which is floating in
the sea water makes very complex motions, so that when the
light-guide cables 13 and 13' are spliced in a conventional manner,
the light-guide cable 13' is subjected to twising forces and is
torn off. In order to prevent such accident, according to the
present invention, the light-guide cables 13 and 13' are spliced
through an optical-guide coupler 30. The coupler 30 receives and
optically connects the light-guide cables 13 and 13' in such a way
that the output end of the light-guide cable 13 and the input end
of the light-guide cable 13' may be rotated with respect to each
other about the extended axis of the vertical shaft 16. In
addition, the buoy 20 is so arranged as to freely rotate about the
light-guide cable 13'.
The solar energy is converted by the photoelectric element 12 into
the electrical energy which is transmitted through lead wires and
slip rings (not shown) to the batteries 22 to charge them. Because
of this efficient charging of the batteries 22, they may supply the
power for turning on a warning lamp 29 and driving the supporting
framework 14 for a considerably long period of operation.
The buoy 20 further includes a dynamotor 25 and turbine wheels 27
and 28. When the turbine wheel 27 is rotated by the tidal wheels or
the like, the dynamotor 24 generates electricity which in turn is
charged into the batteries 22. When the buoy 20 is moved to another
position, the dynamotor 25 is driven as a motor so as to drive the
turbine wheel or screw 28. The buoy 20 further includes hatch
covers 24 for inspection of batteries 22 and an anchor rope or the
like 26 for securing the buoy 20.
As described above, according to the present invention, the solar
energy which is collected through the lens 11 can be supplied in a
very efficient manner through the light-guide cables 13 and 13' to
an underwater farm, ranch or the like. In addition, the
photoelectric element 12 can supply the power required for turning
on the warning lamp 29 and driving the supporting frame 14 and the
dynamotor 25. Furthermore, the optical system for collecting the
solar energy is enclosed in the transparent spherical casing or
dome 17, so that the contamination of the surfaces of the lens 11
and photoelectric element 12 can be avoided. Furthermore the
surfaces of the transparent dome 17 are almost free from
contamination so that the efficient collection of solar energy may
be ensured. Moreover the weight of the collection lens 11 and the
photoelectric element 12 is balanced symmetrically of the center of
the spherical casing or dome 17; that is, the weight is distributed
symmetrically about the horizontal and vertical shafts 15 and 16,
so that the lens 11 and the photoelectric element 12 may be kept
pointed at the sun with a minimum power. As a consequence, a long
service life of the batteries 22 may be ensured and the solar
energy may be collected over a long period of time without
attendance of an operator. Since the buoy 20 can freely rotate
about the light-guide cable 13' which is extended to an underwater
farm, ranch or the like, the light-guide cable 13' may be prevented
from being twisted and torn off even when the waves cause the
irregular movements of the buoy 20.
Second Embodiment, FIGS. 2, 3 and 4
In FIG. 2 is shown in perspective view a second embodiment of a sun
tracking apparatus in accordance with the present invention. A main
shaft 101 is rotated by a motor 102 in the directions indicated by
a double-pointed arrow A, and a shaft 103 is rotatably supported by
a bearing 104 at a right angle to the main shaft 101. A solar
energy collector 105 is mounted on the shaft 103. Therefore as the
shaft 103 is rotated in the directions indicated by a
double-pointed arrow B, the solar energy collector 105 is also
rotated in the same directions as indicated by a double-pointed
arrow B'. A motor 106 which is mounted on the main shaft 101 has
its drive shaft connected to a worm 107 which in turn is in
engagement with a worm wheel 108 mounted on the shaft 103.
At the dawn, the motor 102 is driven so that the main shaft 101 is
rotated in such a way that the solar energy collection apparatus
may be directed to the direction in which the run rises above the
horizon. As the sun rises, the motor 106 is driven so that the
solar energy collectors 105 may be kept pointed at the sun.
Therefore the most efficient collection of solar energy can be
accomplished. As the sun moves, the rotations of the shafts 101 and
103 by the motors 102 and 106 are so controlled that the solar
energy collectors 105 are kept pointed at the sun, whereby they can
collect the solar energy under the most efficient condition.
In FIG. 3 is shown in top view one example of the solar energy
collector 105 while in FIG. 4 is shown in front view the collector
105. The solar energy collector 105 consists of a plurality of
solar energy collection units 105a and 105b which are mounted on
the shaft 103 symmetrically of both the shafts 101 and 103 so that
the turning moments acting on them may become minimum. Each solar
energy collection unit 105a or 105b includes a lens 109 and a solar
energy receiving member 110 located at the focal point of the lens
109.
Third Embodiment, FIGS. 5, 6 and 7
In FIG. 5 is shown in top view a third embodiment of a solar energy
collector in accordance with the present invention. FIG. 6 is a
sectional view taken along the line V--V of FIG. 5 and FIG. 7 is a
side view looking in the direction indicated by the arrow VI in
FIG. 5. The solar energy collector consists of a plurality of solar
energy collection units 105.sub.l through 105.sub.n(n=24) which are
so arranged that their tops form roughy a partial spherical
surface. In addition, the solar energy collection units 105.sub.l
through 105.sub.n are so arranged that the center of gravity of the
solar energy collector 105 coincides with the intersection between
the shafts 101 and 103 so that the turning moments acting on the
latter may become minimum. Furthermore the solar energy collection
units 105.sub.l through 105.sub.n are arranged symmetrical about
the axis of the shaft 101 so that the solar energy collector 105
may be rotated about the axis of the shaft 103 through a large
angle; that is, the range of elevation angle becomes large.
As shown at the left portion in FIGS. 5 through 7, the whole solar
energy collection units 105.sub.l through 105.sub.n may be enclosed
in a transparent casing 111. Alternatively, each solar energy
collection unit 105.sub.n may be sealed individually as indicated
in the right portions in FIGS. 5 through 7. Furthermore the whole
solar energy collector 105 may be contained in the transparent
casing 112 as shown in FIG. 2. Furthermore the whole solar energy
collection apparatus including the shafts 101 and 103, their
associated components and the solar energy collector 105 may be
contained in a suitable casing or housing 113 as shown in FIG.
8.
In the second and third embodiments, the solar energy collection
units 105.sub.n have been described as being elevated or rotated
through the axis of the shaft 103 through the worm 107 and the worm
wheel 108, but it is to be understood that any other suitable means
may be employed. Furthermore it is to be understood to those
skilled in the art that the main shaft 101 is so arranged as to
control the elevation angle while the worm gearing or any other
suitable means may be employed so as to control the azimuth when
the solar energy collection apparatus is installed
horizontally.
Fourth Embodiment, FIGS. 9 and 10
Sector gear pair 121a and 121b whose bases are rotatably carried by
a shaft 120 are interconnected with shafts 122a and 122b and are in
mesh with gears 124a and 124b, respectively, carried by a shaft 123
which in turn is rotated in the direction indicated by a
double-pointed arrow A in FIG. 9 by a motor 125. Therefore when the
shaft 123 is rotated in the clockwise direction in FIG. 9, the
sector gears 121a and 121b are rotated in the counterclockwise
direction, and vice versa as indicated by the double-pointed arrow
A' in FIG. 9.
A shaft 126 whose one end is rotatably supported by the shaft 120
is rotatably supported by the connecting rod 122a as best shown in
FIG. 10. A sector gear 127 whose base is securely attached to the
shaft 126 is in mesh with a worm 131 driven by a motor 128 which in
turn is mounted on the lower connecting rod 122b as best shown in
FIG. 10. The shaft 126 carries solar energy collection units 129a
and 129b. Reference numerals 130 and 130' denote
counterweights.
As the azimuth and elevation of the sun change, the motors 128 and
125 are so driven that the solar energy collector 129 may be
rotated about the axes of the shaft 126 and 120 so as to follow the
diurnal motion of the sun.
The rotation of the shaft 126 can be transmitted through a shaft or
connecting rod 126' to a shaft 126a which is similar in
construction and arrangement with the shaft 126 and carries solar
energy collection units 129'a and 129'b so that all the solar
energy collection units 129 may be angularly controlled
simultaneously. It is apparent to those skilled in the art that in
this manner the number of solar energy collection units may be
increased to as many as desired.
With the solar energy collection apparatus described above with
reference to FIGS. 9 and 10, efficient solar energy collection may
be carried out from sunrise to sunset.
Fifth Embodiment, FIGS. 11 and 12
A fifth embodiment of the present invention will be described below
with reference to FIGS. 11 and 12. A main shaft 201 is so arranged
as to rotate in the direction indicated by the double-pointed arrow
A in FIG. 11 by a driving device 202 which, as will be described in
more detail with particular reference to FIG. 12, comprises a worm
220 driven by a motor or the like (not shown), a worm wheel 221 in
mesh with the gear 220, a sleeve 222 integral with the worm wheel
221 and a torque limiter 223 between the main shaft 201 and the
sleeve 222.
A shaft 203 is rotatably mounted in a bearing 204 which in turn is
mounted on the main shaft 201 at a right angle. A solar energy
collector 205 is carried by the elevation shaft 203. A sector gear
208 which is carried by the shaft 203 is in mesh with a worm 207
which in turn is driven by a motor 206 mounted on the main shaft
201. Therefore, upon rotation of the motor 206, the shaft 203
rotates in the direction indicated by the double-pointed arrow B so
that the solar energy collector 205 is also rotated in the same
direction as indicated by the double-pointed arrow B'.
At sunrise the motor (not shown) is driven to drive the worm 220,
thereby rotating the main shaft 201 so as to point the solar energy
collector 205 in the direction in which the sun rises. As the
azimuth and altitude of the sun change during its diurnal motion,
the motors are so driven that the solar energy collectors 205 may
precisely follow the diurnal motion of the sun from sunrise to
sunset, whereby the very efficient collection of solar energy may
be accomplished.
In this embodiment, the worm gearing is employed so that no torque
will not be transmitted from the main shaft 201 and the worm 207 to
their associated driving devices such as motors. In addition, a
safety device such as a torque limiter is interposed between the
main shaft 201 and the driving device 202 so that when excessive
torques are exterted to the solar energy collection apparatus due
to gusts or the like, the safety device may release the main shaft
201 from the driving device 202.
Referring to FIG. 12, the rotation of the motor (not shown) in
transmitted to the main shaft 201 through the worm 220, the worm
wheel 221, the sleeve 222 extended from the worm wheel 221
coaxially thereof and the torque limiter 223 interposed between the
sleeve 222 and the main shaft 201. Therefore, the rotation of the
main shaft 201 is not transmitted through the worm gearing to the
driving motor (not shown) so that the stable operation of the solar
energy collection apparatus may be ensured.
The use of the worm gearing ensures the stable operation of the
solar energy collection apparatus so that the solar energy
collection apparatus may be kept pointed at the sun in a stable
manner. However, when excessive forces act on the solar energy
collection apparatus due to gusts or the like, the connections or
joints between the solar energy collectors 205 and the worm 220 are
broken if there are not provided suitable shock absorbing means or
the like. The torque limiter 223 is provided in order to prevent
such breakdowns as described above. That is, when the excessive
forces act on the solar energy apparatus, the connection or joint
between the main shaft 201 and the worm gearing may be
released.
Referring to FIG. 12, an engaging means such as a pin 223.sub.c is
inserted into a tapped hole 223.sub.b formed through the
cylindrical wall of the sleeve 222 and a recess 223.sub.a formed in
the cylindrical surface of the main shaft 201. Thereafter a coiled
spring 223.sub.d is inserted into the tapped hole 223.sub.b and
then a screw 223.sub.e is screwed into the tapped hole 223.sub.b.
Therefore the sleeve 222 and the main shaft 201 are joined normally
with the pin 223.sub.c, whereby the rotation of the sleeve 222 is
transmitted to the main shaft 201. However when excessive forces
act on the solar energy collection apparatus due to gusts or the
like, excessive turning moments are exerted to the main shaft 201.
Then the pin 223.sub.c is forced to be pulled out of the recess
223.sub.a and pushed into the tapped hole 223.sub.b against the
coiled spring 223.sub.d, whereby the connection between the main
shaft 201 and the sleeve 222 is released and, consequently, the
main shaft can freely rotate relative to the sleeve 222. Thus the
solar energy collection apparatus can be protected against
breakdowns due to gusts or the like.
The rotation of the sleeve 222, which is connected through the worm
gearing to the driving motor (not shown), is controlled by a
programmed timing device such as a microcomputer (not shown) in
such a way that the solar energy collectors 205 may follow the
diurnal motion of the sun from sunrise to sunset. However, when the
connection between the main shaft 201 and the sleeve 222 is
released as described above, the solar energy collectors 205 cannot
be pointed at the sun. Therefore in order to re-establish the
driving connection between the main shaft 201 and the sleeve 222,
the present invention provides a motor 213. The drive shaft of the
motor 213 carries a gear 214 which is in mesh with a gear 212
mounted on the main shaft 201. After the gust is over, the motor
213 is driven so that the main shaft 201 is rotated. Then the pin
223.sub.c which is pressed against the cylindrical surface of the
main shaft 201 under the force of the coiled spring 223.sub.d drops
into the recess 223.sub.a so that the driving connection between
the main shaft 201 and the sleeve 222 or the worm gearing may be
re-established. Then the motor 213 is stopped. In this case, the
motor 213 may be manually controlled or automatically controlled in
response to the signal from a suitable sensor means for sensing the
angular position of the main shaft 201 relative to the sleeve 222,
the displacement of the pin 223.sub.c or the elastic distortion of
the coiled spring 223.sub.d.
The solar energy collected by the solar energy collectors 205 is
transmitted through a light-guide cable or an optical fiber 210
extended through the main shaft 201 and supported by a supporting
member 211. A light-guide cable or the like 232 is extended through
a pipe 231 coaxially thereof and supported by a supporting member
234. Therefore the light-guide cables 210 and 232 can be optionally
coupled in a very simple manner and the efficient and simple
transmission of the solar energy from the light-guide cable 210 to
the light-guide cable 232 may be ensured. When the solar energy
collected by the collectors 205 is once converted into electrical
energy in the solar energy collection apparatus, instead of the
light-guide cables 210 and 232, the electrical conductors or cables
are employed. In this case when they are extended in a manner
substantially similar to that described above, they may be spliced
together in a very simple manner.
As described above, according to the fifth embodiment of the
present invention, the main shaft 201 of the solar energy
collection apparatus is driven through the worm gearing. As a
result, the transmission of rotation in the opposite direction;
that is, from the main shaft 201 to the driving motor (not shown)
can be avoided so that the solar energy collectors 205 may follow
the diurnal motion of the sun in a very stable manner. In addition,
the torque limiter is interposed between the worm gearing and the
main shaft 201, so that even when the excessive forces suddenly act
on the solar energy collection apparatus due to gusts or the like,
the torque limiter 223 can release the driving connection between
the worm gearing and the main shaft 201 and, consequently, the
breakdowns of the tracking or driving device can be avoided.
Furthermore when the gust is over, the driving connection between
them can be immediately established again so that the tracking can
be started again.
Sixth Embodiment, FIGS. 13 through 17
According to a sixth embodiment to be described in detail below
with reference to FIGS. 13 through 17, the lens or lens system for
collecting the solar energy can follow the diurnal motion of the
sun in such a way that the most efficient solar energy collection
can be attained. However, it is apparent to those skilled in the
art that the sixth embodiment can track not only the sun but also
other celestial bodies such as the moon and objects which reflect
back the light.
Referring first to FIG. 13, the solar energy SL is collected
through a lens such as Fresnel lens 301 and focused upon the input
end of a light-guide cable, a photoelectric element or a
photothermal element. For instance, the collected solar energy is
transmitted through the light-guide cable to a desired location
where it is used for illumination or it is converted into other
useful energies such as electrical or thermal energy.
The lens 301, the solar energy input means 302 and optical sensors
304.sub.x1, 304.sub.x1 ', 304.sub.y1 and 304.sub.y ' to be
described in detail below are mounted on a supporting framework or
the like 303 which in turn is driven so as to follow the diurnal
motion of the sun by a tracking device (not shown).
In order to make the solar energy collection apparatus or collector
follow the diurnal motion of the sun, there has been proposed a
system in which in response to the output from a solar energy
sensor, the whole solar energy collection apparatus; that is, the
supporting framework 303 in this embodiment is made to follow the
diurnal motion of the sun. However this system has a distinct
defect in that once the interception of the sun light by the solar
energy sensor is interrupted by clouds, the tracking is interrupted
and it becomes extremely difficult to have the solar energy
collection apparatus to track the sun again. In order to overcome
this defect, there has been also proposed a system in which based
upon the predicted diurnal motion of the sun, a timing device
controls the tracking of the solar energy collection apparatus or
the supporting frame 303. But this system also has a defect that
whether or not the solar energy collected through the lens 301 is
focused on the solar energy input means 302 cannot be detected. As
a result, the tracking continues with the collected solar energy
not focused on the solar energy input means 302 in the worst
case.
The present invention was made in order to overcome the above and
other problems and defects encountered in the prior art tracking
systems.
Referring further to FIG. 14, at least one pair or preferably two
pairs of optical sensors 304.sub.x1 through 304.sub.y1 ' are
positioned around the coverging square prism S of the solar energy
(when the angle of incidence is zero) and symmetrically about the
axis of the lens 301 between the same and the solar energy input
means 302.
In FIG. 15 is shown the relationship between the angle of incidence
of the solar energy or the sun light falling on the lens 301 and
the position at which the collected solar energy is focused. As is
well known to those skilled in the art of solar energy technology,
when and only when the angle of incidence is 0.degree., the image
of the sun is sharply focused at the solar energy input end 302.
However, as the angle of incidence varies, the point at which the
solar energy is focused (to be referred to as "the focused point"
in this specification) deviates from the solar energy input means
302. For instance, when the incidence angle is 30.degree., the
focused point is at A.sub.30 and the focused point is moved to the
point A.sub.60 when the angle of incidence becomes 60.degree..
Therefore, when the optical sensors 304 are located as shown, the
optical sensor 304.sub.x1 can intercept the light when the angle of
incidence is between 0.degree. and 30.degree. while no light falls
on the optical sensor 304.sub.x1 '. The outputs from these sensors
304.sub.x1 and 304.sub.x1 ' are applied to a differential amplifier
305.sub.x (See FIG. 14) and in response to the output from the
amplifier 305.sub.x a servomotor 306.sub.x is driven so that the
supporting framework 303 may be pointed at the sun. Then the
outputs from the optical sensors 304.sub.x1 and 304.sub.x1 ' become
equal in level so that no output signal is derived from the
differential amplifier 306.sub.x and, consequently, the servomotor
306.sub.x is stopped. In other words, the servomotor 306.sub.x is
so driven that the outputs from the optical sensors 304.sub.x1 and
304.sub.x1 ' and may become equal in level and, consequently, the
framework 303 may be always kept pointed at the sun. As a result,
the efficient collection of solar energy may be ensured.
When the sun is shadowed by clouds, the quantities of the light
incident on both the optical sensors 304.sub.x1 and 304.sub.x1 '
are equal so that the tracking is suspended in a stable manner.
When the sun is exposed again and the angle of incidence is within
30.degree., one of the optical sensors 304.sub.x1 and 304.sub.x1 '
receives the light while the other does not so that the servomotor
306.sub.x is driven again in such a way that the difference in
output between the optical sensors 304.sub.x1 and 304.sub.x1 '
becomes zero.
So far the optical sensors 304 have been described as being
positioned adjacent to the square pyramid of the solar energy
converging toward the solar energy input means 302 as best shown in
FIG. 14, but it is apparent to those skilled in the art that they
may be located within the pyramid S or on the boundaries thereof.
When the optical sensors 304 are positioned as shown in FIG. 14,
the servomotor 306.sub.x is so driven that no light falls upon the
optical sensors 304.sub.x1 and 304.sub.x1 ' as described above and,
consequently, they may be prevented from being damaged or burned by
the solar energy. The optical sensors 304.sub.x1 and 304.sub.x1 '
may be interposed at any positions between the lens 301 and the
solar energy input means 302 as long as their positions are
adjacent to the boundaries of the pyramid of the solar energy
converging toward the solar energy input means 302. In general, the
closer they are located toward the lens 301, the larger the range
for detecting the position of the sun becomes so that the solar
energy collection apparatus may precisely follow the diurnal motion
of the sun. On the other hand, the closer the positions of the
optical sensors 304 toward the solar energy input means 302, the
narrower the sun position detection range becomes, but the solar
energy collection apparatus can follow the diurnal motion of the
sun more precisely. As is apparent from the above description, the
pair of optical sensors 304.sub.x1 and 304.sub.x1 ' are used to
track the sun the azimuthal direction and the provision of another
pair of optical sensors 304.sub.y1 and 304.sub.y1 ', which are
positioned symmetrically about the line connecting the optical
sensors 304.sub.x1 and 304.sub.x1 ', enables the solar energy
collection apparatus to follow the altitude of the sun. Thus, the
solar energy collection apparatus can precisely follow the diurnal
motion of the sun from sunrise to sunset throughout the
seasons.
Seventh Embodiment, FIGS. 16 and 17
A seventh embodiment shown in FIGS. 16 and 17 is substantially
similar in construction to the sixth embodiment described above
with reference to FIGS. 13, 14 and 15 except that an upper array of
optical sensors 304.sub.x1 through 304.sub.y1 ' and a lower array
of optical sensors 304.sub.x2 through 304.sub.y2 ' are provided.
The arrangement of the upper and lower optical sensor arrays is
substantially similar to that of the sixth embodiment, and the
upper array is located in the plane indicated by the line I--I of
FIG. 16 while the lower array in the plane indicated by the line
II--II of FIG. 16. The cross sections of the pyramid of the solar
energy converging toward the solar energy input means 302 which
cross sections are taken on these planes are indicated by S.sub.1
and S.sub.2, respectively, in FIG. 17.
The outputs of the optical sensors 304.sub.x1 and 304.sub.x2 are
applied to the inputs of an OR gate 304.sub.x12 while the outputs
of the optical sensors 304.sub.x1 ' and 304.sub.x2 ' to the inputs
of an OR gate 304.sub.x12 '. The outputs of OR gates 304.sub.x12
and 304.sub.x12 ' are applied to the inputs of the differential
amplifier 305.sub.x. In like manner, the outputs of the optical
sensors 304.sub.y1 and 304.sub.y2 ' are applied to an OR gate
304.sub.y12 ' while the outputs of the optical sensors 304.sub.y1
and 304.sub.y2 to an OR gate 304.sub.y12. The outputs of OR gates
304.sub.y12 and 304.sub.y12 ' are applied to the inputs of the
differential amplifier 305Y. As with the sixth embodiment, the
servomotors 306X and 306Y are driven in response to the outputs,
respectively, from the differential amplifiers 305X and 305Y.
Therefore in response to the outputs from the optical sensors in
the upper array, the rough tracking is accomplished while in
response to the outputs from the optical sensors in the lower array
the fine tracking is accomplished, whereby the solar energy
collection apparatus precisely follow the diurnal motion of the
sun.
Since the optical sensors 304 in the lower array are located closer
to the lens 301, the light of high intensity falls upon them so
that the burning of the optical sensors tends to occur. Therefore
in order to protect them, suitable heat shielding or absorbing
means or optical filters are positioned in front of them. With this
arrangement, it becomes possible to use the optical sensors all of
the same construction and made of the same materials.
In FIG. 17 the outputs of the optical sensors 304.sub.x1 and
304.sub.x2 ; that is, the optical sensors in the upper and lower
arrays but on the same side are shown as being applied through OR
gate 304.sub.x12 to one input of the differential amplifier 305X
while the outputs of the optical sensors 304.sub.x1 ' and
304.sub.x2 ' to the other input of the amplifier 305X through OR
gate 304.sub.x12 ', but it is understood that the signal
representative of the difference in output between the optical
sensors 304.sub.x1 and 304.sub.x1 ' in the same or upper array may
be derived by a first differential amplifier and applied to an OR
gate while, in like manner, the difference in output between the
optical sensors 304.sub.x2 and 304.sub.x2 ' in the same lower array
may be derived by a second differential amplifier and applied to
the same OR gate and that in response to the output from this OR
gate the servomotor 306X may be driven. Same is true for the
tracking sub-system including the optical sensors 304.sub.y for
tracking the altitude of the sun.
So far the seventh embodiment has been described as following the
diurnal motion of the sun, but it is to be understood that the
seventh embodiment may be used for tracking an object which makes
irregular motions.
As described above, the automatic tracking device described above
with reference to FIGS. 16 and 17 can easily track any object which
emits or reflects light and moves or travels in a very wide range.
For instance, even when the automatic tracking device fails to
track a light-emitting object which makes very irregular motion, it
can immediately detect the object and resume the automatic
tracking. Therefore the advantages of the automatic tracking device
are pronounced especially when it is installed on a buoy or the
like which makes very irregular motions because of wave
motions.
Eighth Embodiment, FIG. 18
In the case of the solar energy collection apparatus of the type
shown in FIG. 2, there must be provided a system for correctly
detecting the position of the sun so as to control the azimuth and
altitude or elevation motors 102 and 106, thereby keeping the solar
energy collection apparatus pointed at the sun. The eighth
embodiment of the present invention relates to such system as
described above.
Referring to FIG. 18, a ring 410 is fitted over the main shaft 101
(See FIG. 2) for rotation in the directions indicated by the
double-pointed arrow A. A yoke 412 made of a strip-like material is
pivoted to the ring 410 with pins or arms 411a and 411b for
rotation in the directions indicated by the double-pointed arrow B.
The lower portions of the arms of the yoke 412 are bent inwardly
and a weight 413 is securely attached to the lower ends of the arms
which are joined. As a result, regardless of the rotation and angle
of inclination of the main shaft 101, the yoke 412 is normally
maintained vertically.
A socket 414 is attached at the top of the yoke 412 and receives a
spherical lens 415. A matrix array of optical sensors such as
photo-cell is mounted on the upper surface of the socket 414 or the
lower semi-spherical surface of the spherical lens 415. The
position of the optical sensor which is turned on is dependent upon
the position of the sun so that the position of the sun can be
detected in terms of the position of the optical sensor which is
turned on.
As described above, according to the eighth embodiment of the
present invention, the position of the sun can be detected
precisely so that the solar energy collection apparatus may
precisely follow the diurnal motion of the sun and, consequently,
the efficient solar energy collection may be ensured.
Ninth Embodiment, FIGS. 19 and 20
In FIG. 19 is shown in section a ninth embodiment of a solar energy
collector in accordance with the present invention. In general, the
solar energy collector 501 comprises a lens 501 for collecting the
solar energy L, a supporting framework or lens barrel 503 for
supporting the lens 502, a bottom plate 504 and an optical coupler
505 at which is converged or focused the solar energy and from
which the collected solar energy is transmitted through a
light-guide cable 506. Of these components the present invention
relates particularly to the construction of the optical coupler 505
which enables the solar energy that is collected through the lens
502 to enter the light-guide cable 506 in an efficient manner.
In FIG. 20 is shown in cross section and on enlarged scale the
optical coupler 505 which, in general, comprises a plurality of
light transmission members or layers 505.sub.1 through 505.sub.n
having different refractive indexes. These light transmission
members or layers 505.sub.1 are laminated or stacked from the top
to the bottom in the order to refractive indexes. That is, the top
transmission member or layer 505.sub.1 has the smallest refractive
index; the next light transmission member or layer 505.sub.2 has
the next smallest refractive index and so on and finally the bottom
or lowermost light transmission member 505.sub.n has the greatest
refractive index. As a result, the solar energy focused at the top
surface of the optical coupler 505 is further converged toward the
axis of the optical coupler 505 as indicated by the solid lines in
FIG. 20 and finally enters the light-guide cable 506 at an optimum
angle with respect to the axis thereof.
When the optical coupler were made of a single light transmission
member; that is, when the refractive index of the optical coupler
were same, part of the solar energy falling on it would travel as
indicated by the dotted line and would not be directed toward the
inlet end of the light-guide cable 506, resulting in a considerable
degree of transmission or coupling loss.
Instead of laying the light transmission members or layers one upon
another as shown in FIG. 20, an optical coupler may be made of a
single light transmission member in which a refractive-index
gradient along the axis is so selected that the solar energy may be
gradually converged toward the input end of the light-guide cable
506 and enter into it at an optimum angle with respect to the axis
thereof. Alternatively, a plurality of light transmission members
having different refractive-index gradients may be overlayed one
upon another. Furthermore, a plurality of optical couplers of the
types described above may be coupled in series.
As described above, according to the ninth embodiment or the
optical coupler in accordance with the present invention, the
collected solar energy may be fed into the light-guide cable 506 in
a very efficient manner.
Prior Art Light-Guide Cable, FIG. 21
In FIG. 21 is shown in cross section of a conventional light-guide
cable consisting of a plurality of optical fibers 506.sub.l through
506.sub.n circular in cross section. Therefore when the light-guide
cable 506 is coupled to the optical coupler of the type shown in
FIG. 19, the solar energy also enters the spaces between the
optical fibers 506.sub.l through 506.sub.n and between them and the
cladding, resulting in the loss of collected solar energy. The dead
space between the optical fibers and between them and the cladding
is dependent upon the thickness of the cladding and becomes as high
as about 30% of the cross sectional area of the light-guide cable
506.
Tenth Embodiment, FIG. 22
A tenth embodiment of the present invention which was made to
overcome the above problem will be described in detail with
reference to FIG. 22. The cladding of the light-guide cable 606 is
removed a predetermined length from the input end of the cable 606
so as to expose the optical fibers 606.sub.l through 606.sub.n
hexagonal in cross section and stranded also hexagonal in cross
section. As a result, when the input end of the light-guide cable
606 is optically coupled to the optical coupler 505 of the type
shown in FIG. 20, no transmission loss occurs between them because
there exists no dead space between the optical fibers and between
them and the cladding.
In order to remove the cladding and to make the optical fibers
606.sub.l through 606.sub.n to have a hexagonal cross section, the
cladding adjacent to the input end of the light-guide cable 606 is
heated and melted to such a degree that the exposed optical fibers
may not be melted. Thereafter a suitable jig or wire is applied to
the heated end of the light-guide cable 606 in such a way that the
softend or melted cladding may be removed and the exposed strand of
optical fibers may be forcibly shaped to have a hexagonal cross
section. As a consequence the individual optical fibers are forced
to reduce its circular cross section to a substantially hexagonal
cross section and are forced into very intimate contact with each
other.
So far the solar energy collected through the lens 502 has been
described as being fed into the light-guide cable 606 through the
optical coupler 505, but it is to be understood that the solar
energy may be directly focused through the lens 502 at the input
end of the light-guide cable 606. In addition, the optical coupler
505 may be used for optically splicing the light-guide cables or
the like.
As described above, according to the tenth embodiment of the
present invention, by the simple end preparation consisting of the
steps of removing the cladding of the light-guide cable 606 a
predetermined length from the input end thereof and molding the
exposed optical fibers into a hexagonal cross section, the solar
energy collected through the lens 502 can be fed through the
optical coupler 505 into the light-guide cable 606 in a very
efficient manner. In addition, the end-to-end connection between
the light-guide cables can be accomplished in a very efficient
manner.
Joints for Light-Guide Cables for End-to-End Connection or
Branching, FIGS. 23 through 30
When the light-guide cables are joined for end-to-end connections
or branching with the use of conventional connectors or couplers
and splitters in order to give certain desired properties to the
network of light-guide cables and other components, considerable
degrees of transmission losses occur in the connectors or couplers
and splitters. Some embodiments to be described below with
particular reference to FIG. 23 through 30 relate to the
improvements of the joints for light guides which may facilitate
the end-to-end connection between the light-guide cables and the
branching or splitting of the light-guide cables and which may
reduce the transmission losses at the joints to a negligible
degree.
In FIG. 23 is shown a layout of light-guide cables in accordance
with the present invention. The solar energy L collected by a solar
energy collector generally indicated by the reference numeral 701
is transmitted through a light-guide network to desired locations
where the solar energy is used for, for instance, illumination. As
described elsewhere, the solar energy collector 701 comprises a
lens 702, a framework 703 and a bottom plate 704 for supporting the
lens 702 and an optical coupler 705 for entering the collected
solar energy into a light-guide cable 706 which may be directly
extended to a desired remote place or which may be connected
through a connector or coupler 707 end-to-end to another
light-guide cable 708 or, even though not shown, may be splitted
into a plurality of branches.
When the light-guide cables 706 and 708 are connected through the
connector or coupler 707, the alignment between them is very
difficult because the conventional light-guide cables have, in
general, a circular cross section. Furthermore with the
conventional connector or coupler, a considerably higher degree of
transmission losses results. In order to solve these problems, the
present invention teaches to process the ends of the light-guide
cables to be coupled in the manner described above with reference
to FIG. 22. However, it is still difficult to reduce the
transmission losses to a negligible degree. Furthermore, it is
difficult to connect one light-guide cable to a plurality of
light-guide cables at the same joint. The present invention may
substantially overcome these problems as will become apparent from
the following description.
Referring to FIGS. 24 and 25, the light-guide cables used in the
present invention are in general flat or thin rectangular in cross
section may be, "rectangular in cross section" is correct, and the
coupler or connector 707 is of the half lap joint type or the
mortise-and-tendon type or the combination thereof. One or lower
major surface cladding 706.sub.a of the light-guide cable 706 is
removed to expose its core 706.sub.b and teeth 706.sub.2 through
706.sub.2n triangular in cross section are formed in the core
706.sub.b. In like manner, one or upper major surface cladding
708.sub.a of the light-guide cable 708 is removed to expose its
core 708.sub.b and teeth 708.sub.l through 708.sub.(2n+1) of the
shape adapted to snugly mate with the teeth of the light-guide
cable 706 are formed in the core. The mortise or joint of the
light-guide cable 706 and the tenon or joint of the light-guide
cable 708 may have any suitable cross section such as a rectangular
or square or sinusoidal cross section (See FIG. 26).
FIG. 27 is a longitudinal sectional view taken along the line V--V
of FIG. 25 and showing the joint 707 between the light-guide cables
706 and 708. First the teeth of the light-guide cables 706 and 708
are snugly engaged with each other, and then an optically
transparent compound 709 is melted and poured into the space
between the teeth of the light-guide cable 708. Thereafter a
lift-reflection film or coating 710 is applied over the transparent
compound 709, and a protective layer 711 is formed.
The solar energy is transmitted from the light-guide cable 706 into
the light-guide cable 708 through the interface therebetween. Some
of the solar energy transmitted through the light-guide cable 706
is reflected by the reflecting film 710 so as to enter the
light-guide cable 708.
In FIGS. 28 and 29 is shown a modification of the joint 707
described above with reference to FIGS. 24 through 27. The ends to
be joined of the light-guide cables 706 and 708 can be prepared in
the same manner, and the cables 706 and 708 can be joined in a very
simple manner without the above-described additional steps of
filling the transparent compound 709, forming the reflecting film
710 and applying the protective coating 711.
So far the light-guide cable 706 has been described as being joined
to the single light-guide cable having the same cross section as
the cable 706, but it is to be understood that the light-guide
cable 706 may be joined to a plurality of light-guide cables in a
manner substantially similar to that described above. That is, the
end to be joined of the light-guide cable 706 is enlarged in cross
section so as to afford the connection to a plurality of
light-guide cables. Alternatively, the ends of the light-guide
cables to be connected to the light-guide cable 706 are reduced in
cross section.
So far the light-guide cable 706 has been described as being
connected to one or more light-guide cables straightly or in
series, but it is to be understood that the light-guide cable 706
can be branched to the light-guide cable 708 as shown in FIG.
30.
The light-guide cables which are joined in the manner described
above may be fabricated by the injection molding so that they may
have the same cross section throughout their whole lengths.
Alternatively, the ends of the commercially available light-guide
cables may be heated and molded to have the desired cross
sections.
In summary, when the light-guide cables in accordance with the
present invention the light-guide cables can be joined or branched
in a very simple manner and the transmission losses may be made
almost negligible. In addition, one light-guide cable can be joined
to one or more light-guide cables in a very simple manner.
* * * * *